The Human Rights Campaign just released its annual Corporate Equality Index, highlighting the best places for LGBT people to work in the United States. A record 304 major corporations earned a perfect score of 100 on this year's CEI, meaning that those companies offer full benefits to same-sex domestic partners, have nondiscrimination policies that are inclusive of sexual orientation and gender identity, offer trans-inclusive healthcare plans, host regular LGBT-inclusive diversity trainings, and have a public commitment to the LGBT community.

"This will go down in history as the year that corporate support for equality left the boardroom and reached each and every corner of this country," said HRC president Chad Griffin in a release announcing the report. "Not only do fair-minded companies guarantee fair treatment to millions of LGBT employees in all 50 states, but now those same companies are fighting for full legal equality in state legislatures, in the halls of Congress, and before the U.S. Supreme Court."

Griffin's reference to the Supreme Court is a nod to the more than 300 companies and law firms that filed legal briefs in support of marriage equality when the nation's highest court considered two landmark cases this summer — and ruled in favor of equality in both cases. On a more administrative level, an impressive 91 percent of Fortune 500 companies have workplace nondiscrimination policies that are inclusive of sexual orientation, while 61 percent have extend those protections to trans and gender-nonconforming people.

Read the full report (in PDF form) here, and click through to find out which of the top 20 Fortune 500 companies earned perfect scores on this year's CEI.

Click through to find the 13 top-rated corporations among the Fortune 20. >>>